EVOLUTION OF MAIZE ROOT DISTRIBUTION IN SPACE-TIME DURING MAIZE VARIETIES REPLACING IN CHINA

Field and limited soil cylinder cultivation of widely grown maize cultivars released from 1950s to 1990s in China was conducted in order to investigate differences in the growth of the root system through space and time. Dry matter accumulation of maize roots agreed with a Vapor Pressure Model. Root weight of 1990s cultivars increased rapidly as plants grew and a long period of high root weight continued from anthesis until maturity; this trend became more evident with deeper soil. 1990s maize cultivars root weight in 40 100 cm soil depth were 75% and 1060% higher than those of 1970s and 1950s, respectively; the proportion of roots in this layer was also much higher. The percentage of roots that were located within a horizontal area 0 10 cm soil from the plant center was also higher than in cultivars of 1970s and 1950s. We conclude that the historical development in maize cultivars has led to increased vertical extension and horizontal contraction.